A ram boring machine having a two-part housing, i.e. having a housing tip screwed into the housing accommodating the striking piston, is known from DE-PS 21 57 259. There the housing tip surrounds a chisel having its front end, in the working or striking direction, formed as a striking tip and having at its other end a collar and a shank or pin, the collar being accommodated by a bore in the front housing. The shank represents the striking face for the associated striking piston and, in the starting position before the working stroke, projects from a ring screwed into the housing with the housing tip. The ring limits the movement of the collar, and thus that of the chisel, counter to the working direction of the striking tip. The movement of the chisel in the working direction is limited by a front stop formed by a shoulder in the bore of the housing tip accommodating the collar. The chisel is supported by the collar and compression springs on the housing tip; the springs move the chisel back after each blow from its front position in the housing tip, in the working direction, to its starting position. Besides the ram boring machine with the two-part housing just described, ram boring machines in which the housing and the housing tip are integral are also known; otherwise there are no significant differences between a two-part and a one-part machine housing.
It has been found, particularly if the known machines are used in soft ground, that rebounding blows cannot be avoided. While in the case of hard ground the chisel and thus its striking tip is not moved forward from its starting position, possibly even against the force of a spring, so far that the collar could reach the shoulder of the housing bore limiting the chisel movement, soft ground in comparison does not give as much resistance. The collar thus strikes the front stop defined by the shoulder of the housing bore and owing to the impact energy of the striking piston the undesired rebounding blows thus occur.